At the scene of a major fire there is a need for quick visual identification of each firefighter. Ideally, the identification is carried on the helmets worn by the firefighters. Reflexite Corporation of New Britain, Conn., currently sells retroreflective stickers for this purpose. Although their retroreflectivity initially affords good visibility, even in smoky areas; when exposed to heat and flames they readily melt, char, and lose their retroreflectivity and, after being so exposed, they are difficult to remove to permit application of fresh stickers. Other decals or labels are believed to have been used for marking fire helmets, but insofar as is known, they catch on fire when exposed to flames or the heat of a fire and the resulting char is difficult to remove.
U.S. Pat. No. 4,533,592 (Bingham) is concerned with making firefighters more visible under firefighting conditions. The patent discloses a fluorescent fabric (for good daytime visibility) that is partially covered by retroreflective sheeting (for nighttime visibility), which fabric does not char or melt when held in a forced air oven at 260.degree. C. for 5 minutes, and has a char length less than 10.2 centimeters as measured by U.S. Fed. Test Method Standard 191, Textile Test Methods, Method 5903.
The Minnesota Mining and Manufacturing Company ("3M") currently sells retroreflective sheeting that is flame and heat resistant as SCOTCHLITE Brand Retroreflective Fabric No's. 8486, 8487, 8930, 8986, and 8987. These fabrics are sold as sew-on fabrics and do not possess adhesive backings.
Markings that are applied to hard substrates such as firefighter's helmets which are typically made of strong polycarbonate can not be sewn thereon. There exists a need for markings that can be securely attached to such substrates and that can subsequently be readily removed therefrom, even after exposure to high temperature and flame.